With the increasing need to dissipate heat that is generated within microelectronic, electronic, telecommunication and electric devices, thermally conductive elastomeric materials are becoming increasingly important to the overall performance of electronic device packages. Key components that provide heat dissipation in such devices include, for example, thermal interface materials (e.g., thermal pads, thermal gels, etc.) and heat conductive rubber seals, among others. High temperature resistant materials such as silicone rubber, fluoroelastomers (FPM), and thermally conductive elastomeric materials are often used for such components to dissipate and effectively manage heat that is generated within electronic devices.
Thermally conductive fillers, which can also be electrically insulating or electrically conductive, are typically added to an elastomeric material to increase thermal conductivity (Tc). Depending on the target Tc, a high volume of filler is usually needed to form the network needed to convert an elastomer material from essentially a heat insulator to a thermally conductive material. However, a high volume fraction of inorganic filler is known to have a negative effect on other properties of the elastomer material such as softness, compression set, compound viscosity, etc. In addition, there are increased costs associated with the use of a high volume of thermally conductive fillers.
Fillers, such as graphite and boron nitride, are preferred materials that generally provide a high intrinsic thermal conductivity (Tc) at a relatively low loading. Graphite and boron nitride have a layered, planar micro-structure. Typically, the layers are stacked in parallel and thus form platelet shaped particles. Atoms in the layer plane are bonded covalently, whereas bonding between layers is via weak Van der Waals bonds. Therefore, these fillers have intrinsically anisotropic (directionally dependent) thermal conductivity. When added to an elastomer material during flow processing, they tend to orient and provide a much higher Tc in the plane (or flow) direction than in the thickness direction of the material. However, a high Tc in the thickness direction of a conductive elastomer component (e.g., thermal interface pad) is crucial to heat dissipation in a device construction.
It would, therefore, be desirable to provide a thermally conductive elastomeric material that has a low filler content and/or with a high thermal conductivity (Tc) at a given filler loading in a thickness direction of the material or component.